Conventional shotshell ammunition for firing from a shotgun has a hull that includes a metal cup-shaped structure defining a closed firing end of the ammunition, and a cylindrical portion that extends from the metal cup-shaped structure. A primer is provided at the firing end of the ammunition in an aperture extending through the cup-shaped structure. Gun powder is disposed within the hull within the metal cup-shaped structure and adjacent the primer. One or more projectiles are disposed within a sabot, and the sabot is disposed within the hull adjacent the gun powder such that the gun powder is disposed in a space between the metal cup-shaped structure of the hull and the sabot with the projectile(s) therein. As used herein, the term “sabot” means a structure in which a projectile is carried through a barrel of a firearm and which separates from the projectile upon exiting the barrel of the firearm. The projectile may include a plurality of generally spherical rounded pellets, which are often referred to as the “shot” of the ammunition. The cylindrical portion of the hull is typically formed of plastic, and an end of the plastic cylindrical portion of the hull opposite the metal cup-shaped structure is mechanically deformed (by rolling, folding, etc.) and crimped to close the end of the ammunition (opposite the firing end of the ammunition) from which the sabot (and the one or more projectiles carried therein) exits the hull upon firing of the ammunition.
In conventional shotshell ammunition, the cylindrical portion of the hull has a maximum outer diameter that is smaller than a maximum outer diameter of the metal cup-shaped structure defining the closed firing end of the ammunition. Thus, the cup-shaped structure includes or defines a rim that projects outwardly in the radial direction beyond the outer surface of the cylindrical portion of the hull, and, in some previously known ammunition, a portion of the metal-cup-shaped structure having a reduced outer diameter. Conventional shotguns include a seat surface that is configured to abut against the metal rim at the firing end of the ammunition so as to prevent longitudinal forward movement of the hull within the shotgun when the shotshell type ammunition is loaded into and fired from the shotgun.